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Old 22nd September 2005, 06:19 AM   #11
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Default Re: how to clean our ac power??

Quote:
Originally posted by tube shop
how to clean our ac cable and ac power
Buy a big >5kW EI core (not torroid/R) isolation transformer on the surplus market. It will act as a low pass filter and clear out a lot of the noise in the system.
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Old 22nd September 2005, 06:29 AM   #12
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Hello Everyone,
If I suffered a problem my AC supply to the point where I couldn't enjoy my music anymore, I would go out and buy as many 12Volt car batteries as would be needed to power my amplifier and bypass the transformer all together. I would change them at night or set up a trickle charger setup and disconnect the mains power when I wanted to listen to my Amplifier.
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Old 22nd September 2005, 03:41 PM   #13
Tweeker is offline Tweeker  United States
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Theres issues with using lead acid batteries indoors.


Also, while they may be DC, they arent especially clean DC from what I read here at TNT Audio.
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Old 22nd September 2005, 04:16 PM   #14
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Default Re: Re: how to clean our ac power??

Quote:
Originally posted by Brett
Buy a big >5kW EI core (not torroid/R) isolation transformer on the surplus market. It will act as a low pass filter and clear out a lot of the noise in the system.
there's a tradeoff between the leakage inductance which mitigates spikes and the capacitance between primary and secondary which likes to pass them along.

DC offset -- this should serve to heat the core of the transformer -- and those types of problems. Have you checked for a ground fault, possible corroded ground connection between the fuse box and ground?
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Old 22nd September 2005, 05:06 PM   #15
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I have a 12.5 amp 1500 VA EI core isolation transformer. Is this large enough to be of value? My understanding is that an EI transformer forms a low pass filter and so gets rid of lots of the RF "junk" that is riding on the incoming AC.

Should I try it?

Also, what happens if there is a sudden interruption to the AC service to my home? Will the transformer's magnetic field unload and send a dangerous spike to my attached electronics? If I use it should I include a husky MOV across its output?

Thanks
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Old 22nd September 2005, 05:15 PM   #16
mzzj is offline mzzj  Finland
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Quote:
Originally posted by Tweeker
Theres issues with using lead acid batteries indoors.


Also, while they may be DC, they arent especially clean DC from what I read here at TNT Audio.
As said before, there is something really wrong in that measurement as it is generating loads of 50hz disturbance. Real performance of lead-acids remains to be seen until someone makes a bit more believable measurement.
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Old 22nd September 2005, 05:43 PM   #17
Eva is offline Eva  Spain
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The high frequency AC signals present in any mains line may be subdivided in two groups: Common mode and differential mode.

Common mode signals appear between both phase and neutral, and earth, and they are easily radiated by wiring. Therefore, even an isolation transformer won't filter them at all due to inter-winding capacitance, but a common mode choke will do a great job.

Differential mode signals appear between phase and neutral, and will be gently filtered by any LF transformer, including the ones from the power supplies of aduio equipment, so they are a minor concern.
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Old 22nd September 2005, 05:59 PM   #18
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Could you not get a very clean mains electromechanically?

I mean say, buy two reasonably sized electric motors and then mechanically couple them together. One takes power from the mains and then feeds it mechanically to the second.

You could couple them with a solid bushing but there's more chance of higher frequencies getting from A -> B with that. Better would be a belt between the two.

Not much high frequency noise should make it through the system as it is. But if you wanted to get classy I guess you could add a really heavy flywheel to the second motor's spindle so it takes a minute or two to spin up. If you're using valves you're going to have to wait for them to warm up anyway right?

I'm only thinking of that because I have buckets of lead spare I'm trying to think of a use for.

Adding a big heavy flywheel should blast away transients from the mains.

Now you'd have your own localised AC generator, powered from the normal mains but highly isolated from it.

If the flywheel was heavy enough it might even ride over brown outs quite well on it's own. You definitly wouldn't have to worry about reactive spikes as magnetics lost and regained power.

You could scoop the motors second hand from somewhere; use your imagination.

I only thought of it because you could end up spending quite a lot of money and time on a perfected electronic filter, so the motor idea's quirkyness starts becoming more acceptable.

Obviously have to situate the device in the garage or something and run a line in.

If you buy a three phase machine tool and want to use it on single phase at home you can either buy a solid state variable frequency converter or mechanically couple two motors together, one suited to the machine's motor and the other to your mains. Roughly the same idea just for a different reason.

I'm not suggesting this as a majorly serious idea, just a thought.

If you're really into audio, would like a clean line and are considering a huge bank of 12V batteries I guess it's not so bad.
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Old 22nd September 2005, 06:38 PM   #19
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Quote:
Originally posted by eeka chu
adding a big heavy flywheel should blast away transients from the mains.
we are using flywheel based energy storage systems in the US for critical applications -- sort of liked pumped storage -- i would like to know how much the bearings cost in one of those babies.
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Old 22nd September 2005, 06:51 PM   #20
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Quote:
Originally posted by jackinnj

we are using flywheel based energy storage systems in the US for critical applications -- sort of liked pumped storage -- i would like to know how much the bearings cost in one of those babies.
Yep, I've heard of that; big mechanical batteries.

The bearings are usually magnetic I think.

I believe they're quite common in orbiting satellites. Since satellites are in a super low zero gravity enviroment to start with when you add magnetic bearings you end up with an incredibly low loss system.

I imagine the bearings are quite expensive but not excessively so. A normal contact bearing is probably as expensive. The bearings in these don't need to be ultra precise they just have to be low drag.

The most expensive bearings are probably the magnetic ones used in machine tool spindles as they need to be both whilst resisting extremely high deflection forces.

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